It is often desirable to reshape the opening of a container body that is open on one end (i.e., an “open ended container body”) during the process of manufacturing a container. One example of such reshaping is a process known as “necking” in which the diameter of the container body opening is reduced in order, for example, to allow the use of a smaller diameter lid or end for the container. In another example of reshaping, a “flanging” process may be employed to form a flange on the container open end. Flanges are often used to facilitate attachment of a lid to a container body. Other exemplary reshaping operations may involve expansion or the formation of features such as threads on a portion of the container body.
In a die necking operation, the open end of a typically cylindrical, thin walled metal container body is forcefully brought into contact with a die having a smaller diameter than the open end of the container body. Contact between the container body open end and the die, in this manner, results in a reduction in diameter of the open end. In a progressive die necking operation, the container body open end is forced into a series of progressively smaller dies in order to achieve a progressive reduction in diameter of the open end. In a typical die necking operation, a knockout element (sometimes also referred to as a “knockout punch” or a “knockout die”) may be used to provide support, during the necking operation, to the inside diameter of the open end of the container body. Methods and apparatus for die necking containers are disclosed, for example, in U.S. Pat. No. 5,355,710 of Diekhoff and U.S. Pat. No. 5,768,931 of Gombas, both of which are hereby incorporated by reference herein for all that is disclosed therein.